Peptide pharmaceutical for oral delivery

ABSTRACT

Acid-containing oral pharmaceutical compositions are provided wherein the pharmaceutical active agents are peptide compounds (i.e., those that include a plurality of amino acids and at least one peptide bond in their molecular structures). Certain barrier layers and/or particulate coated acid are used to reduce any adverse interactions that might otherwise occur between the acid of the compositions and other components of the composition. Use of these barrier layers and/or use of particulate coated acid is believed to promote a more simultaneous release of the components of the composition than is achieved by prior art acid-protection techniques, thus enhancing, and making more consistent, the bioavailability of the active peptide compounds.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application claims priority of U.S. Provisional Application Ser.No. 60/940,598 filed May 29, 2007, the disclosure of which isincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to acid-containing oral peptidepharmaceutical compositions wherein the pharmaceutical active agents arepeptide compounds (i.e. those that include a plurality of amino acidsand at least one peptide bond in their molecular structures), andparticularly to the use of certain barrier layers and/or particulatecoated acid to reduce adverse interactions that might otherwise occurbetween the acid of the compositions and other components of thecomposition. Use of these barrier layers and/or use of particulatecoated acid is believed to enhance stability of the composition, andfollowing administration, to promote a more simultaneous release of thecomponents of the composition than is achieved by prior artacid-protection techniques. This enhances, and makes more consistent,the bioavailability of the active peptide compounds.

2. Description of the Related Art

Numerous human hormones, neurotransmitters and other importantbiological compounds have peptides as a substantial part of theirmolecular structures. Many diseases respond positively to raising thelevel of these peptide compounds in patients. Therapeutically effectiveamount of such biologically relevant peptides may be administered topatients in a variety of ways. However, as discussed further below,preferred oral administration is very difficult with this type of activecompound.

Salmon calcitonin, for example, is a peptide hormone which decreasesuptake of calcium from bone. When used to treat bone-related diseasesand calcium disorders (such as osteoporosis, Paget's disease,hypercalcemia of malignancy, and the like), it has the effect of helpingmaintain bone density. Many types of calcitonin have been isolated(e.g., human calcitonin, salmon calcitonin, eel calcitonin, elkatonin,porcine calcitonin, and chicken calcitonin). There is significant lackof structural homology among the various calcitonin types. For example,there is only 50% percent identity between the amino acids making uphuman calcitonin and those making up salmon calcitonin. Notwithstandingthe difference in molecular structure, salmon calcitonin may be used inthe human treatment of the calcitonin-responsive diseases discussedabove.

Peptide pharmaceuticals used in the prior art frequently have beenadministered by injection or by nasal administration. Insulin, forexample, is one of many peptide pharmaceuticals frequently administeredby injection. A more preferred oral administration tends to beproblematic because peptide active compounds are very susceptible todegradation in the stomach and intestines. Salmon calcitonin, forexample, lacks sufficient stability in the gastrointestinal tract, andtends to be poorly transported through intestinal walls into the blood.However, injection and nasal administration are significantly lessconvenient than, and involve more patient discomfort than, oraladministration. Often this inconvenience or discomfort results insubstantial patient noncompliance with a treatment regimen. Thus, thereis a need in the art for more effective and reproducible oraladministration of peptide pharmaceuticals.

Proteolytic enzymes of both the stomach and intestines may degradepeptides, rendering them inactive before they can be absorbed into thebloodstream. Any amount of peptide that survives proteolytic degradationby proteases of the stomach (typically having acidic pH optima) is laterconfronted with proteases of the small intestine and enzymes secreted bythe pancreas (typically having neutral to basic pH optima). Specificdifficulties arising from the oral administration of a peptide likesalmon calcitonin and other peptides discussed herein involve therelatively large size of the molecule, and the charge distribution itcarries. This may make it more difficult for the peptide to penetratethe mucus along intestinal walls or to cross the intestinal brush bordermembrane into the blood. These additional problems may furthercontribute to limited bioavailability.

In U.S. Pat. No. 6,086,918 (Stern et al), peptides were delivered orallyusing a multi-component system which included, inter alia, significantquantities of acid useful in lowering intestinal pH and hence theactivity of intestinal proteases that have neutral or basic pH optima.For best results in prior art pharmaceuticals of this type, it ispreferred that the several components of the system be released into theintestines as close to simultaneously as possible. Uniform dispersion ofthe many components of the composition can aid this objective. However,interaction of the acid with the peptide active agent is preferablyavoided, and prior art attempts to reduce interaction between acid andpeptide active agent frequently resulted in less uniform dispersion ofthe various components or otherwise tended to make release of allcomponents less simultaneous. This, in turn, harmed peptidebioavailability, as well as consistency of that bioavailability from oneadministration to the next, either in the same subject or from onesubject to the next.

U.S. Patent Publication No. 2003/0017203 (Crotts et al) discloses awater-soluble coating that substantially prevents contact between apH-lowering agent in a pharmaceutical formulation and an outer entericcoating. That publication, however, discloses a laminate structurewherein active peptide and an absorption enhancer are in one layer ofthe laminate, while acid is in another. This desirably helps reduceinteraction of peptide with pharmaceutical acid, and interaction ofabsorption enhancer with pharmaceutical acid, but makes consistent,reproducible, and near-simultaneous release of all components moredifficult. Acid can also interact unfavorably with other components ofthe pharmaceutical composition. A bilayer structure, however, providesphysical separation of components whose complexity may result in aundesirable variability in dissolution that the present invention seeksto reduce.

Prior art acid-containing oral peptide pharmaceuticals frequently usedenteric coatings to separate peptide active agents from stomachproteases. Enteric coating does not dissolve in the acid environment ofthe stomach, but dissolves readily in the basic environment of theintestines, thus desirably targeting an intestinal release. Anotherproblem caused by the significant acid levels of prior artacid-containing oral peptide pharmaceuticals is slower or unevendissolution of the enteric coating in the intestines. This is believedto be because the high acid content of the composition can interferewith the desirable quick dissolution of the enteric coating by creatinglocalized acid environment (in which enteric coating does not dissolve)even in the generally basic environment of the intestines. As notedabove however, prior art attempts to avoid interaction between acid andother components of the pharmaceutical composition have themselves hadundesirable effects on the simultaneity of release of the variouspharmaceutical components. Variability of dissolution may undesirablycontribute to variability of bioavailability.

There is therefore a need in the art for acid-containing oral peptidepharmaceutical compositions wherein the interactions between acid andother components can be minimized, while still maintaining goodnear-simultaneous release of the various components.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to better preventundesirable effects of acid on peptide active agents and/or entericcoatings while maintaining good dissolution profiles wherein allingredients of the oral pharmaceutical composition are released into theintestines in close time proximity, thus enhancing bioavailability.

It is a further object to provide a therapeutically effective oralpharmaceutical composition for reliably and consistently deliveringpharmaceutical peptides when administered orally.

It is a further object of the invention to provide therapeutic oralcompositions containing peptide active agents having good and consistentbioavailability.

In one embodiment, the invention provides a pharmaceutical compositionfor oral delivery of a physiologically active peptide agent comprising:

(A) said peptide agent;

(B) at least one pharmaceutically acceptable acid wherein said acid ispresent in said pharmaceutical composition in a quantity which, if saidcomposition were added to 10 milliliters of 0.1M aqueous sodiumbicarbonate solution, would be sufficient to lower the pH of saidsolution to no higher than 5.5;

(C) an acid-resistant protective vehicle (e.g., enteric coating)effective to transport said pharmaceutical composition through thestomach of a patient while preventing contact between said activepeptide agent and stomach proteases; and

(D) a water soluble barrier layer that separates said acid from saidprotective vehicle;

wherein either (a) said barrier layer adds 3-6% to the weight of thepharmaceutical composition, exclusive of any acid-resistant protectivevehicle, or (b) said barrier layer comprises a material having watersolubility in excess of 11 grams per 100 milliliters of water at roomtemperature, or (c) said peptide agent and said acid are in the same oronly layer of said composition.

In another embodiment, the invention provides a pharmaceuticalcomposition for oral delivery of a physiologically active peptide agentcomprising said active peptide agent, and pharmaceutically acceptableacid particles that are coated with a pharmaceutically acceptableprotective coating that is non-acidic and has a solubility in water ofat least one gram per 100 milliliters of water at room temperature;wherein total acid in said pharmaceutical composition is in a quantitywhich, if said composition were added to ten milliliters of 0.1M aqueoussodium bicarbonate solution, would be sufficient to lower the pH of saidsolution to no higher than 5.5.

In another embodiment, the invention provides a pharmaceuticalcomposition for oral delivery of a physiologically active peptide agentcomprising:

(A) said peptide agent;

(B) at least one pharmaceutically acceptable acid wherein said acid ispresent in said pharmaceutical composition in a quantity which, if saidcomposition were added to 10 milliliters of 0.1M aqueous sodiumbicarbonate solution, would be sufficient to lower the pH of saidsolution to no higher than 5.5, wherein said acid comprises acidparticles that are coated with a pharmaceutically acceptable protectivecoating that is non-acidic and has a solubility in water of at least onegram per 100 milliliters of water at room temperature;

(C) an acid resistant protective vehicle effective to transport saidpharmaceutical composition through the stomach of a patient whilepreventing contact between said active peptide agent and stomachproteases; and

(D) a water soluble barrier layer that separates said coated acid fromsaid protective vehicle;

wherein either (a) said barrier layer adds at least 3% to the weight ofthe pharmaceutical composition, exclusive of any acid-protectivevehicle, or (b) said barrier layer comprises a material having watersolubility in excess of one gram per 100 milliliters of water at roomtemperature, or (c) said peptide agent and said acid are in the same oronly layer of said composition.

Without intending to be bound by theory, it is believed that, when thepharmaceutical composition of the invention is administered to subjects,significant quantities of acid are released by the composition in closetime proximity with release of the peptide active agent. This reducesthe activity of neutral to basic-acting proteases (e.g. luminal ordigestive protease and proteases of the brush border membrane) bylowering pH below the optimal activity range of these proteases. Thus,the peptide active agents are less vulnerable to proteolytic degradationuntil they can be successfully transported into the bloodstream. Withoutintending to be bound by theory, it is believed that the materials andstructures of the pharmaceutical compositions herein reduce adverseinteractions between the acid of the compositions and the othercomponents of the composition. It is further believed that theinventions herein promote a more simultaneous release of the componentsof the composition than is achieved by prior art acid-protectiontechniques, thus enhancing, and making more consistent, thebioavailability of the active peptide compounds.

The pharmaceutical compositions of the invention have both human andveterinary applications. Any animal having neutral to basic-actingproteases in the digestive tract should benefit from the invention'smore-simultaneous release of significant quantities of acid togetherwith the peptide active agent.

Other features and advantages of the present invention will becomeapparent from the following detailed, and non-limiting, description ofcertain preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a comparison of the dissolution profiles of pharmaceuticaltablets containing coated acid particles versus uncoated acid.

FIG. 2 is a sectional view of a pharmaceutical tablet that utilizes theembodiment of the invention relating to a protective barrier layer thatcan enhance dissolution of an enteric coating where enteric coatings areused. The figure shows the relative positions of the protective barrier,enteric coating and reminder of the pharmaceutical composition in onepreferred embodiment. FIG. 2 is not necessarily to scale, and is onlyfor the purpose of illustrating preferred relative locations of variouslayers. The preferred percentages of material used in the various layersare discussed elsewhere herein.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The present invention includes use of significant quantities of acid toimprove bioavailability of peptide pharmaceutical active agents astaught in U.S. Pat. No. 6,086,918, the entire disclosure of which isincorporated by reference herein.

In accordance with the invention, patients in need of treatment withpeptide active ingredients are provided with an oral pharmaceuticalcomposition thereof (at appropriate dosage), preferably but notnecessarily in tablet or capsule form of an ordinary size in thepharmaceutical industry. The dosages and frequency of administering theproducts are discussed in more detail below. Patients who may benefitare any who suffer from disorders that respond favorably to increasedlevels of a peptide-containing compound. For example, oral salmoncalcitonin in accordance with the invention may be used to treatpatients who suffer from calcium disorders or bone diseases. Theinvention may be used, for example, to treat osteoporosis, Paget'sdisease, hypercalcemia of malignancy and the like, with oral calcitonin,preferably salmon calcitonin.

Salmon calcitonin is a preferred active ingredient for use in accordancewith the invention for a number of reasons. For example, it provides anumber of advantages over even human calcitonin, even when used as apharmaceutical agent for human patients. Among the advantages providedby utilizing salmon calcitonin instead of human calcitonin for thetreatment of human osteoporosis are increased potency, analgesia andincreased half-life. Also, lower dosages are necessary than with humancalcitonin. There is substantial non-homology between salmon and humancalcitonin, with only 50% identity in the amino acid sequences of thetwo calcitonins. Notwithstanding the foregoing preference for salmoncalcitonin, other calcitonins and other peptides (discussed in moredetail, infra) may be used in accordance with the invention.

Because the oral delivery provided by the pharmaceuticals hereinenhances protection of the peptide active agents from proteolyticdegradation, it is expected to increase bioavailability of a wide rangeof therapeutic peptide active agents that would otherwise be more proneto proteolytic degradation. A separate section below discusses thevarious peptide active agents.

Not all embodiments of the invention include an acid protective vehiclesuch as an outer layer of enteric coating. Such vehicles are desirablefor enhancing bioavailability, but can slow uptake of the activeingredients into the bloodstream. Thus, in time-sensitive medicalapplications, for example, pain relief, there can be some advantage insacrificing some bioavailability in return for faster delivery in thebloodstream. For use in medical applications where bioavailability isdeemed more important than speed, use of an acid protective vehicle ispreferred.

In embodiments that utilize an acid protective vehicle, quick anduniform dissolution of that vehicle in the intestines may be facilitatedby keeping the acid of the composition away from said vehicle during itsdissolution. This may be accomplished in accordance with the inventionin one of two ways (or in certain preferred embodiments by utilizingboth techniques). First, the use of a protective barrier layer betweenthe acid protective vehicle and the acid of the pharmaceuticalcomposition can enhance the more simultaneous release of allpharmaceutical composition in the intestines by permitting most of theenteric coating to dissolve in the intestines before the acid of thepharmaceutical composition is released or otherwise comes in contactwith the acid protective vehicle. Otherwise the acid could adverselyaffect the dissolution of the protective vehicle (which is insoluble inacid environment). This barrier layer is expected to provide thisbenefit regardless of the form in which the acid is supplied, and evenwhen coated acid particles (used in other embodiments of the invention)are not present. Details regarding preferred materials and thicknessesfor the protective barrier layer are discussed infra in a sectiondirected to this layer.

Alternatively, the acid of the composition may be provided in the formof coated acid particles. The coating on these particles is apharmaceutically acceptable protective coating that is non-acidic andhas a solubility in water of at least one gram per 100 milliliters ofwater at room temperature. In addition to desirably separating thepharmaceutical acid from the pharmaceutical active peptide, this coatingon the acid particles may help protect the pharmaceutical composition'senteric coating (or other acid protective vehicle) from the undesirableeffects acid can have on quick uniform dissolution of the outer coatingin the intestines. This is true even in embodiments of the inventionthat do not include the protective barrier layer. In some, but not all,embodiments of the invention, both (1) the protective barrier layer ispresent, and (2) the acid is supplied, at least in part, in the form ofcoated acid particles.

Likewise, providing acid to the pharmaceutical composition in the formof the foregoing coated acid particles provides numerous advantages thatare independent of any effect on enteric coating, and independent ofwhether or not a protective barrier layer is used. Such coated acidparticles may therefore be used advantageously even in embodiments ofthe invention that include neither outer coating of acid protectivevehicle, nor protective barrier layer. In particular, acid in the formof coated particles may desirably be thoroughly intermixed with thepeptide active agent, while undesirable acid-peptide interaction isminimized. Without intending to be bound by theory, this thoroughintermixing is believed to facilitate simultaneous release of eachcomponent together so that acid may better protect the peptide, in theintestinal environment, by reducing peptide degradation from theactivity of local proteases having neutral or basic pH optima.

In some but not all embodiments, an absorption enhancer, as described inmore detail in a separate section, infra, is included in thepharmaceutical composition to further enhance bioavailability. In onepreferred embodiment, coated acid particles, peptide active agent,absorption enhancer, acid protective vehicle and protective barrierlayer are all present. The use of coated acid particles, in addition toreducing undesirable acid interactions with other components discussedherein, desirably reduces acid interaction with absorption enhancer(when used) or with surfactant (when used).

In one preferred embodiment, coated acid, peptide and, optionally, oneor more of any optional components discussed herein, e.g. an absorptionenhancer, are thoroughly intermixed. The mixture is then coated withboth a protective barrier layer and an outer acid-protective vehicle.One version of this embodiment is illustrated by FIG. 2, a sectionalview of an embodiment utilizing a pharmaceutical tablet 5. As shown inFIG. 2, a water-soluble barrier layer 20 preferably lies just inside ofan acid protective vehicle layer 30, and separates vehicle layer 30 fromthe intermixed remaining contents 10. FIG. 2 shows the relativepositions of the water-soluble barrier layer, acid-protective vehicleand remaining ingredients. FIG. 2 is not necessarily to scale, and isonly for the purpose of illustrating preferred relative locations ofvarious layers. The preferred percentages of material used in thevarious layers are discussed elsewhere herein.

The acid protective vehicle preferably constitutes an outermostprotective layer surrounding the remainder of the pharmaceuticalcomposition. The vehicle does not dissolve in the acidic stomachenvironment, thus protecting the active peptide components from stomachproteases. Without intending to be bound by theory, it is believed that,later, in the basic pH environment of the intestines, the vehicledissolves quickly without interference from the pharmaceutical acid fromwhich the vehicle is separated by either the barrier layer, or thecoating on the acid particles, or both. It is believed that, once theprotective vehicle dissolves, the water-soluble barrier layer and thecoating surrounding the acid particles quickly release the remainingcomponents of the composition in close time proximity.

The acid is believed to lower the local intestinal pH (where the activeagent has been released) to levels below the optimal range for manyintestinal proteases. It is believed that this decrease in pH reducesthe proteolytic activity of the intestinal proteases, thus affordingprotection to the peptide from potential degradation. The activity ofthese proteases is diminished by the temporarily acidic environmentprovided by the invention. It is preferred that sufficient acid beprovided that local intestinal pH is lowered temporarily to 5.5 orbelow, preferably 4.7 or below and more preferably 3.5 or below. Thesodium bicarbonate test described infra (in the section captioned “thepH-Lowering Agent”) is indicative of the required acid amount.Preferably, conditions of reduced intestinal pH persist for a timeperiod sufficient to protect the peptide agent from proteolyticdegradation until at least some of the peptide agent has had anopportunity to cross the intestinal wall into the bloodstream.Optionally, absorption enhancers, when used, may synergistically promotepeptide absorption into the blood while conditions of reducedproteolytic activity prevail. Preferred absorption enhancers and theiruse are discussed in more detail in a separate section, infra.

It is important that acid and peptide (and, when present, absorptionenhancer) are released together to the extent possible. The acid is thenbetter able to protect the peptide by reducing degradation of peptide byaction of neutral or basic-acting proteases until the peptide crossesthe intestinal wall into the bloodstream. A near-simultaneous release ofabsorption enhancer (when used) can further enhance that crossing of theintestinal wall. In a preferred tablet form of the invention, additionaloptional materials, discussed in separate sections infra, aid in formingtablets of appropriate hardness that resist breaking prior toadministration, and undergo consistent fast and complete dissolution atthe appropriate time after administration. It is important that tabletsor capsules resist formation of “ghosts,” partially intact tablets orcapsules that remain from incomplete dissolution.

The mechanism by which the invention is believed to accomplish the goalof enhanced bioavailability is aided by having active components of thepharmaceutical composition released together as simultaneously aspossible. To this end, in embodiments where an acid-resistant protectivevehicle is used, it is preferred to keep the volume of theacid-resistant protective vehicle as low as possible consistent withproviding protection of the peptide active agent from stomach proteases.Thus, the acid-resistant protective vehicle is less likely to interferewith peptide release, or with the release of other components in closetime proximity with the peptide. The acid-resistant protective vehicleshould normally add less than 30% to the weight of the remainder ofpharmaceutical composition (i.e., the other components of thecomposition excluding the acid-resistant protective vehicle).Preferably, it is less than 20% and, more preferably, the entericcoating adds between 10% and 20% to the weight of the uncoatedingredients. When a water-soluble barrier layer is used in addition tothe acid-resistant protective vehicle, less acid-resistant protectivevehicle may be required. In some such embodiments, a weight gain of from4-10%, or in some embodiments 4-7% is provided by the acid-resistantprotective vehicle. A water-soluble protective barrier layer between theacid protective vehicle and the pharmaceutical acid or other contents ofthe composition preferably adds at least a 3% weight gain to thecomposition. In some embodiments, it adds 3-6%. In some preferredembodiments, the amount of water-soluble barrier layer exceeds theamount of acid-protective vehicle.

In embodiments in which an absorption enhancer is optionally used, theenhancer, which may be a solubility enhancer and/or transport enhancer(as described in more detail below), aids transport of the peptide agentfrom the intestine to the blood, and may promote the process so that itbetter occurs during the time period of reduced intestinal pH andreduced intestinal proteolytic activity. Many surface active agents mayact as both solubility enhancers and transport (uptake) enhancers. Againwithout intending to be bound by theory, it is believed that enhancingsolubility desirably provides (1) a more simultaneous release of theactive components of the invention into the aqueous portion of theintestine, (2) better solubility of the peptide in, and transportthrough, a mucous layer along the intestinal walls. Once the peptideactive ingredient reaches the intestinal walls, an uptake enhancerprovides better transport through the brush border membrane of theintestine into the blood, via either transcellular or paracellulartransport. As discussed in more detail below, many preferred compoundsmay provide both functions. In those instances, preferred embodimentsutilizing both of these functions may do so by adding only oneadditional compound to the pharmaceutical composition. In otherembodiments, separate absorption enhancers may provide the two functionsseparately.

Components of preferred pharmaceutical compositions of the invention,including preferred optional components, are discussed in separatesections below. Species suggested for each component can be used aloneor in combination with other species. For example, combinations ofmultiple pH-lowering agents, or (where an absorption enhancer is used)multiple enhancers can be used as well as using just a singlepH-lowering agent and/or single enhancer. Some preferred combinationsare also discussed below. One or more optional components may beincluded in combination with other optional components.

Peptide Active Ingredients

Peptide active ingredients which may benefit from oral delivery inaccordance with the invention include any therapeutic agent that isphysiologically active and has, as part of its molecular structure, aplurality of amino acids and at least one peptide bond. In preferredembodiments of the invention, degradation of the active ingredients byprotease is suppressed by several mechanisms that would otherwise tendto cleave one or more of the peptide bonds of the active ingredient. Inaddition to natural amino acids, the amino acids may be D-amino acids orunnatural amino acids, some examples of which are discussed infra. Themolecular structure may further include other substituents ormodifications. For example, salmon calcitonin, a preferred peptideactive agent herein, is amidated at its C-terminus. Some peptides may beamidated at locations that are not amidated in nature, or may beotherwise modified.

Peptide active compounds of the invention include, but are not limitedto, insulin, vasopressin, calcitonin (including not only the preferredsalmon calcitonin, but other calcitonins as well). Other examplesinclude calcitonin gene-related peptide, parathyroid hormone (includingamidated or unamidated truncates thereof such as PTH1-31-amide),desmopressin, luteinizing hormone-releasing factor, erythropoietin,tissue plasminogen activators, human growth hormone,adrenocorticototropin, various interleukins, enkephalin, and the like.Many others are known in the art. It is expected that any pharmaceuticalcompound having peptide bonds which would be subject to cleavage in thegastrointestinal tract would benefit from oral delivery in accordancewith the present invention because of the reduction in such cleavagethat is afforded by the present invention.

Both man-made and natural peptides can be orally delivered in accordancewith the invention. Thus, the peptide active compound, in someembodiments, could be glucagon-like peptide—1 (GLP-1), or analogsthereof, desmopressin (DDAVP), leuprolide,2,6-dimethyltyrosine-D-arginine-phenylalanine-lysine amide (DMT-DALDA),peptidomimetics and the like.

When salmon calcitonin is used, it preferably comprises from 0.02 to 0.2percent by weight relative to the total weight of the overallpharmaceutical composition (exclusive of any acid-resistant protectivecoating). Salmon calcitonin is commercially available (for example, fromBACHEM, Torrence, Calif.). Alternatively it may be synthesized by knownmethods, some of which are discussed briefly below. Other peptide activeagents should be present at higher or lower concentrations depending ondesired target blood concentrations for the active compound and itsbioavailability in the oral delivery system of the invention.

When salmon calcitonin is used as an active agent, salmon calcitoninprecursors may be made by either chemical or recombinant syntheses knownin the art. Precursors of other amidated peptide active agents may bemade in like manner. Recombinant production is believed significantlymore cost effective. Precursors are converted to active salmoncalcitonin by amidation reactions that are also known in the art. Forexample, enzymatic amidation is described in U.S. Pat. No. 4,708,934 andEuropean Patent Publications 0 308 067 and 0 382 403. Recombinantproduction is preferred for both the precursor and the enzyme thatcatalyzes the conversion of the precursor to salmon calcitonin. Suchrecombinant production is discussed in Biotechnology, Vol. 11(1993) pp.64-70, which further describes a conversion of a precursor to anamidated product. The recombinant product reported there is identical tonatural salmon calcitonin, and to salmon calcitonin produced usingsolution and solid phase chemical peptide synthesis. Production ofsalmon calcitonin or other amidated products may also be accomplishedusing the process and amidating enzyme set forth by Consalvo, et al inU.S. Patent Publication 2006/0127995; Miller et al, U.S. PatentPublication 2006/0292672; Ray et al, 2002, Protein Expression andPurification, 26:249-259; and Mehta, 2004, Biopharm. International,July, pp. 44-46.

The production of the preferred recombinant salmon calcitonin (rsCT) mayproceed, for example, by producing glycine-extended salmon calcitoninprecursor in E. coli as a soluble fusion protein withglutathione-S-transferase. The glycine-extended precursor has amolecular structure that is identical to active salmon calcitonin exceptat the C-terminal (where salmon calcitonin terminates-pro-NH₂, while theprecursor terminates -pro-gly). An alpha-amidating enzyme described inthe publications above catalyzes conversion of precursors to salmoncalcitonin. That enzyme is preferably recombinantly produced, forexample, in Chinese Hamster Ovary (CHO) cells), as described in theBiotechnology and Biopharm. articles cited above. Other precursors toother amidated peptides may be produced in like manner.

Peptide active agents that do not require amidation may also be producedin like manner, but without the amidation step. Some peptide activeagents are commercially available. Those that are not may be produced bytechniques known in the art.

The pH-Lowering Agent (Acid)

The total amount of the pH-lowering compound to be administered witheach administration of salmon calcitonin should preferably be an amountwhich, when it is released into the intestine, is sufficient to lowerthe local intestinal pH substantially below the pH optima for proteasesfound there. The quantity required will necessarily vary with severalfactors including the type of pH-lowering agent used (discussed infra)and the equivalents of protons provided by a given pH-lowering agent. Inpractice, the amount of pH-lowering agent expected to provide goodbioavailability is an amount which, if the pharmaceutical composition ofthe invention were added to a solution of 10 milliliters of 0.1M sodiumbicarbonate, would lower the pH of that sodium bicarbonate solution tono higher than 5.5, and preferably no higher than 4.7, most preferablyno higher than 3.5. The foregoing test for sufficient acidity isreferenced elsewhere herein as “sodium bicarbonate test” and assumessufficient passage of time for substantially complete dissolution of thepharmaceutical composition and intermixing thereof with the sodiumbicarbonate solution. Enough acid to lower pH, in the sodium bicarbonatetest, to about 2.8 may be used in some embodiments. Preferably at least200 milligrams, and more preferably at least 300 milligrams (sometimes400 milligrams) of the pH-lowering agent are used in the pharmaceuticalcomposition of the invention. The foregoing preferences relate to thetotal combined weight of all pH-lowering agents where two or more ofsuch agents are used in combination. The pharmaceutical composition ofthe invention should not include an amount of any base which, whenreleased together with the pH-lowering compound, would prevent the pH ofthe above-described sodium bicarbonate test from dropping to 5.5 orbelow.

The pH-lowering agent of the invention may be any pharmaceuticallyacceptable compound that is not toxic in the gastrointestinal tract andis capable of either delivering hydrogen ions (a traditional acid) or ofinducing higher hydrogen ion content from the local environment. It mayalso be any combination of such compounds. It is preferred that at leastone pH-lowering agent used in the invention have a pKa no higher than4.2, and preferably no higher than 3.0. It is also preferred that the pHlowering agent have a solubility in water of at least 30 grams per 100milliliters of water at room temperature. In some embodiments, organicacids are used.

Examples of compounds that induce higher hydrogen ion content includealuminum chloride and zinc chloride. Pharmaceutically acceptabletraditional acids include, but are not limited to acid salts of aminoacids (e.g. amino acid hydrochlorides) or derivatives thereof. Examplesof these are acid salts of acetylglutamic acid, alanine, arginine,asparagine, aspartic acid, betaine, carnitine, carnosine, citrulline,creatine, glutamic acid, glycine, histidine, hydroxylysine,hydroxyproline, hypotaurine, isoleucine, leucine, lysine,methylhistidine, norleucine, ornithine, phenylalanine, proline,sarcosine, serine, taurine, threonine, tryptophan, tyrosine and valine.

Other examples of useful pH-lowering compounds include carboxylic acidssuch as acetylsalicylic, acetic, ascorbic, citric, fumaric, glucuronic,glutaric, glyceric, glycocolic, glyoxylic, isocitric, isovaleric,lactic, maleic, oxaloacetic, oxalosuccinic, propionic, pyruvic,succinic, tartaric, valeric, and the like.

Other useful pH-lowering agents that might not usually be called “acids”in the art, but which may nonetheless be useful in accordance with theinvention are phosphate esters (e.g., fructose 1, 6 diphosphate, glucose1, 6 diphosphate, phosphoglyceric acid, and diphosphoglyceric acid).CARBOPOL® (Trademark BF Goodrich) and polymers such as polycarbophil.

Any combination of pH lowering agents that achieves the required pHlevel of no higher than 5.5 in the sodium bicarbonate test discussedsupra may be used. One preferred embodiment utilizes, as at least one ofthe pH-lowering agents of the pharmaceutical composition, an acidselected from the group consisting of citric acid, tartaric acid and anacid salt of an amino acid.

Regardless of the acid chosen, it is preferred to use acid particlescoated with a protective coating discussed in a separate section, infra.

When salmon calcitonin is the peptide active agent, it is preferred thatthe weight ratio of pH-lowering agent to salmon calcitonin exceed 200:1,preferably 800:1 and most preferably 2000:1.

Optional Components

As used herein, a component is considered “optional” if it is notrequired by one or more of the patent claims hereto.

Optional Water Soluble Barrier Layer

When a water soluble barrier layer is used, it is preferred that it becomprised of a compound that is water soluble in both acidic and basicenvironments. Examples of compounds useful for this purpose include butare not limited to hydroxypropylmethylcellulose, hydroxypropylcellulose,methylcellulose and polyvinylpyrolidone. Preferably, water solubility isat least one gram, more preferably at least 11 grams, per 100milliliters at room temperature. Polyvinylpyrolidone is preferred insome embodiments. In some embodiments water solubility, at both pH 6.0and pH 8.0, is in excess of 12 grams per 100 milliliters of water atroom temperature. Good solubility in both acid and basic pH aidsdesirable quick dissolution in the intestinal region where pH isgenerally basic, but where the pharmaceutical composition's release ofsignificant quantities of acid might at least temporarily impededissolution of a material that was not also readily soluble in anaqueous acid environment. The water-soluble barrier layer is preferablyused in embodiments wherein the composition includes an acid-resistantprotective vehicle as its outer layer (for protecting the peptide activeagent from stomach proteases). While the existence of such a vehicledoes not require use of a water-soluble barrier layer, it is preferredto use one, preferably one that is non-ionic (to reduce undesirableinteraction with the acid-protective vehicle). Preferably, thewater-soluble barrier layer adds at least 3% to the weight of thepharmaceutical composition (exclusive of any acid-resistant protectivevehicle), especially 3-6%. In some embodiments the amount of watersoluble barrier exceeds the amount of acid-resistant protective vehicle.

Optional Coated Acid Particles

It is preferred that the acid be provided, at least in part, by acidparticles coated with a protective coating to reduce undesirable acidinteraction with other components of the formulation, such as thepeptide active agent and, where used, the outer enteric coating. Whencoated acid particles are used, the particles are coated with apharmaceutically acceptable protective coating that is non-acidic andpreferably has a solubility in water of at least one gram, andpreferably at least 10 grams, per 100 milliliters of water at roomtemperature. As the coating is for the purpose of reducing acidinteraction with other components of the pharmaceutical composition, itis important that the coating not itself be acidic such that its ownacidity could undesirably cause some of the acid interactions that it isthe coating's purpose to prevent. Good water solubility is alsoimportant for quick dissolution, which in turn desirably aids a moresimultaneous release of the pharmaceutical acid and the peptide activeagent (and when optionally used, the absorption enhancer).

Appropriate coating materials include but are not limited to sugars(e.g. glucose), and acid salts (e.g. sodium citrate). When acid saltsare used, it is preferred, but not required, that they be salts of theacid being coated (e.g., sodium citrate-coated citric acid particles).Preferred coated acid particles include but are not limited toglucose-coated citric acid particles available from Jungbunzlauer underthe trademark CITROCOAT. When used as the acid, citric acid or otherorganic acids can be coated by spraying a coating solution whichcontains, for example, glucose or sodium citrate onto granules of anorganic acid in a fluid-bed dryer. Coatings discussed herein may be usedon particles of other acids discussed herein. Glucose-coated citric acidhas proven to provide good dissolution properties as shown in Examples1-3, infra.

Preferred average size of the acid-coated particles is from 30 mesh to140 mesh.

Optional Absorption Enhancer

It is preferred that an absorption enhancer be included in thepharmaceutical composition. The absorption enhancers are preferablypresent in a quantity that constitutes from 0.1 to 20.0 percent byweight, relative to the overall weight of the pharmaceutical composition(exclusive of any enteric coating). Preferred absorption enhancers aresurface active agents which act both as solubility enhancers and uptakeenhancers. Generically speaking, “solubility enhancers” improve theability of the components of the invention to be solubilized in eitherthe aqueous environment into which they are originally released or intothe lipophilic environment of the mucous layer lining the intestinalwalls, or both. “Transport (uptake) enhancers” (which are frequently thesame surface active agents used as solubility enhancers) are those whichfacilitate the ease by which peptide agents cross the intestinal wall.

One or more absorption enhancers may perform one function only (e.g.,solubility), or one or more absorption enhancers may perform the otherfunction only (e.g., uptake), within the scope of the invention. It isalso possible to have a mixture of several compounds some of whichprovide improved solubility, some of which provide improved uptakeand/or some of which perform both functions. Without intending to bebound by theory, it is believed that uptake enhancers may act by (1)increasing disorder of the hydrophobic region of the membrane exteriorof intestinal cells, allowing for increased transcellular transport; or(2) leaching membrane proteins resulting in increased transcellulartransport; or (3) widening pore radius between cells for increasedparacellular transport.

Surface active agents are believed to be useful both as solubilityenhancers and as uptake enhancers. For example, detergents are useful in(1) solubilizing all of the active components quickly into the aqueousenvironment where they are originally released, (2) enhancinglipophilicity of the components of the invention, especially the peptideactive agent, aiding its passage into and through the intestinal mucus,(3) enhancing the ability of the normally polar peptide active agent tocross the epithelial barrier of the brush border membrane; and (4)increasing transcellular and/or paracellular transport as describedabove.

When surface active agents are used as the absorption enhancers, it ispreferred that they be free flowing powders for facilitating the mixingand loading of capsules during the manufacturing process. Because ofinherent characteristics of salmon calcitonin and other peptides (e.g.,their isoelectric point, molecular weight, amino acid composition, etc.)certain surface active agents interact best with certain peptides.Indeed, some can undesireably interact with the charged portions ofsalmon calcitonin and prevent its absorption, thus undesireablyresulting in decreased bioavailability. It is preferred, when trying toincrease the bioavailability of salmon calcitonin or other peptides thatany surface active agent used as an absorption enhancer be selected fromthe group consisting of (i) anionic surface active agents that arecholesterol derivatives (e.g., bile acids), (ii) cationic surface agents(e.g., acyl carnitines, phospholipids and the like), (iii) non-ionicsurface active agents, and (iv) mixtures of anionic surface activeagents (especially those having linear hydrocarbon regions) togetherwith negative charge neutralizers. Negative charge neutralizers includebut are not limited to acyl carnitines, cetyl pyridinium chloride, andthe like. It is also preferred that the absorption enhancer be solubleat acid pH, particularly in the 3.0 to 5.0 range.

One especially preferred combination, when salmon calcitonin is thepeptide active agent, is a mixture of cationic surface active agents andanionic surface active agents that are cholesterol derivatives, both ofwhich are soluble at acid pH.

A particularly preferred combination is an acid soluble bile acidtogether with a cationic surface active agent. An acyl carnitine andsucrose ester is a good combination. When a particular absorptionenhancer is used alone, it is preferred that it be a cationic surfaceactive agent. Acyl carnitines (e.g., lauroyl carnitine), phospholipidsand bile acids are particularly good absorption enhancers, especiallyacyl carnitine. Anionic surfactants that are cholesterol derivatives arealso used in some embodiments. It is the intent of these preferences toavoid interactions with the peptide agent that interfere with absorptionof peptide agent into the blood.

To reduce the likelihood of side effects, preferred detergents, whenused as the absorption enhancers of the invention, are eitherbiodegradable or reabsorbable (e.g. biologically recyclable compoundssuch as bile acids, phospholipids, and/or acyl carnitines), preferablybiodegradable. Acyl carnitines are believed particularly useful inenhancing paracellular transport. When a bile acid (or another anionicdetergent lacking linear hydrocarbons) is used in combination with acationic detergent, salmon calcitonin is better transported both to andthrough the intestinal wall.

Preferred absorption enhancers include: (a) salicylates such as sodiumsalicylate, 3-methoxysalicylate, 5-methoxysalicylate and homovanilate;(b) bile acids such as taurocholic, tauorodeoxycholic, deoxycholic,cholic, glycholic, lithocholate, chenodeoxycholic, ursodeoxycholic,ursocholic, dehydrocholic, fusidic, etc.; (c) non-ionic surfactants suchas polyoxyethylene ethers (e.g. Brij 36T, Brij 52, Brij 56, Brij 76,Brij 96, Texaphor A6, Texaphor A14, Texaphor A60 etc.), p-t-octyl phenolpolyoxyethylenes (Triton X-45, Triton X-100, Triton X-114, Triton X-305etc.) nonylphenoxypoloxyethylenes (e.g. Igepal CO series),polyoxyethylene sorbitan esters (e.g. Tween-20, Tween-80 etc.); (d)anionic surfactants such as dioctyl sodium sulfosuccinate; (e)lyso-phospholipids such as lysolecithin andlysophosphatidylethanolamine; (f) acylcarnitines, acylcholines and acylamino acids such as lauroylcarnitine, myristoylcarnitine,palmitoylcarnitine, lauroylcholine, myristoylcholine, palmitoylcholine,hexadecyllysine, N-acylphenylalanine, N-acylglycine etc.; g) watersoluble phospholipids such as diheptanoylphosphatidylcholine,dioctylphosphatidylcholine etc.; (h) medium-chain glycerides which aremixtures of mono-, di- and triglycerides containing medium-chain-lengthfatty acids (caprylic, capric and lauric acids); (i)ethylene-diaminetetraacetic acid; (j) cationic surfactants such ascetylpyridinium chloride; (k) fatty acid derivatives of polyethyleneglycol such as Labrasol, Labrafac, etc.; and (l) alkylsaccharides suchas lauryl maltoside, lauroyl sucrose, myristoyl sucrose, palmitoylsucrose, etc.

In some preferred embodiments, and without intending to be bound bytheory, cationic ion exchange agents (e.g. detergents) are included toprovide solubility enhancement by another possible mechanism. Inparticular, they may prevent the binding of salmon calcitonin or otherpeptide active agents to mucus. Preferred cationic ion exchange agentsinclude protamine chloride or any other polycation.

Optional Acid-Resistant Protective Vehicle

It is preferred that an acid-resistant protective vehicle be utilized toseparate the peptide active agent from stomach proteases. Any carrier orvehicle that protects the peptide from stomach proteases and thendissolves so that the other ingredients of the invention may be releasedin the intestine is suitable. Many such enteric coatings are known inthe art, and are useful in accordance with the invention. Examplesinclude cellulose acetate phthalate, hydroxypropyl methylethylcellulosesuccinate, hydroxypropyl methylcellulose phthalate,carboxylmethylethylcellulose and methacrylic acid-methyl methacrylatecopolymer. In some embodiments, the active peptide, absorption enhancerssuch as solubility and/or uptake enhancer(s) (when included), andpH-lowering agent(s), are included in a sufficiently viscous protectivesyrup to permit protected passage of the components of the inventionthrough the stomach.

Suitable enteric coatings for protecting the peptide agent from stomachproteases may be applied, for example, to capsules after the remainingcomponents of the invention have been loaded within the capsule. Inother embodiments, enteric coating is coated on the outside of a tabletor coated on the outer surface of particles of active components whichare then pressed into tablet form, or loaded into a capsule, which isitself preferably coated with an enteric coating.

It is very desirable that all components of the invention be releasedfrom the carrier or vehicle, and solubilized in the intestinalenvironment as simultaneously as possible. It is preferred that thevehicle or carrier release the active components in the small intestinewhere uptake enhancers that increase transcellular or paracellulartransport are less likely to cause undesirable side effects than if thesame uptake enhancers were later released in the colon. It isemphasized, however, that the present invention is believed effective inthe colon as well as in the small intestine. Numerous vehicles orcarriers, in addition to the ones discussed above, are known in the art.It is desirable (especially in optimizing how simultaneously thecomponents of the invention are released) to keep the amount of entericcoating low. Preferably, the enteric coating adds no more than 30% tothe weight of the remainder of pharmaceutical composition (the“remainder” being the pharmaceutical composition exclusive of entericcoating itself). More preferably, it adds less than 20%, especially from12% to 20% to the weight of the uncoated composition. The entericcoating preferably should be sufficient to prevent breakdown of thepharmaceutical composition of the invention in 0.1N HCl for at least twohours, then capable of permitting complete release of all contents ofthe pharmaceutical composition within thirty minutes after pH isincreased to 6.3 in a dissolution bath in which said composition isrotating at 100 revolutions per minute. In embodiments in which thewater-soluble barrier layer of the invention is used, less entericcoating may be required, sometimes less that the amount of water-solublebarrier layer.

Optional Filler

It is preferred that a filler such as a cellulose filler like PROSOLV™available from JRS Pharma be utilized. Other fillers are known in theart.

Optional Pharmaceutical Binder For Dry Compression

It is preferred that the pharmaceutical composition be in tablet formand that a pharmaceutical binder for dry compression be included in thepharmaceutical composition. Preferred binders include but are notlimited to KOLLIDON VA64, KOLLIDON VA64 fine, KOLLIDON 30, AVICELPH-101, PHARMACOAT 606, and MALDEX. The first three are commerciallyavailable from BASF, and the latter three are available from FMCBiopolymer, Shin-Etsu, and Amylum, respectively.

To improve simultaneous release, thorough intermixing of the componentsof the pharmaceutical composition (other than any optional entericcoating or barrier layer) results in substantially uniform dispersion ofsaid components within the binder. For this purpose, coated acidparticles (when used) are considered a single component. It isespecially preferred that acid (or when used, coated acid particles) andpeptide active agent be uniformly dispersed.

Optional Pharmaceutical Disintegrant

In some embodiments, a pharmaceutical tablet is used as a preferreddosage form. Preferably, a pharmaceutically acceptable disintegrant isincluded. Any disintegrant that performs the function of enhancingdissolution speed may be used. Preferred disintegrants include but arenot limited to POLYPLASDONE, EXPLOTAB, and AC-DI-SOL, available fromInternational Specialty Products, JRS Pharma and FMC Biopolymer,respectively. Preferably, the disintegrant is present in an amountbetween 1 and 15 percent by weight relative to the total tablet weight(when tablets are used), exclusive of any water-soluble barrier layerand any acid-resistant protective vehicle.

Optional Pharmaceutical Glidant

In preferred embodiments, a pharmaceutically acceptable glidant isincluded. Any glidant that performs the function of enhancing powderflow may be used. Preferred glidants include but are not limited totalc, calcium silicate, magnesium silicate, silicon dioxide. Preferably,the glidant is present in an amount between 0.1 and 2.0 percent byweight relative to the weight of the pharmaceutical composition,exclusive of any water-soluble barrier layer and any acid-resistantprotective vehicle.

Optional Pharmaceutical Lubricant

In preferred embodiments, a pharmaceutically acceptable lubricant isincluded. Any lubricant that performs the function of preventing powderfrom sticking to the tooling may be used. Preferred lubricants includebut are not limited to stearic acid, magnesium stearate, andhydrogenated vegetable oil type 1. Preferably, the lubricant is presentin an amount between 0.5 and 5.0 percent by weight relative to theweight of the pharmaceutical composition, exclusive of any water-solublebarrier layer and any acid-resistant protective vehicle.

Optional Antioxidant

In some preferred embodiments, a pharmaceutically acceptable antioxidantis included. Any antioxidant that performs the function of preventingthe oxidation of labile amino acids in peptides, such as methionine ortryptophan may be used. Preferred antioxidants include but are notlimited to sodium pyruvate, derivatives of sodium pyruvate, ascorbicacid, ascorbyl palmitate, butylated hydroxyanisole, butylatedhydroxytoluene, sodium bisulfite, and sodium metabisulfite. Preferably,the antioxidant is present in an amount between 0.5 and 5 mg per tablet.

Miscellaneous Other Optional Ingredients

In some preferred embodiments, another peptide (such as albumin, casein,soy protein, other animal or vegetable proteins and the like) isincluded to reduce non-specific adsorption (e.g., binding of peptide tothe intestinal mucus barrier) thereby lowering the necessaryconcentration of the expensive peptide active agent. When added, thepeptide is preferably from 1.0 to 10.0 percent by weight relative to theweight of the overall pharmaceutical composition (excluding anywater-soluble barrier layer and any acid-resistant protective vehicle).Preferably, this second peptide is not physiologically active and ismost preferably a food peptide such as soybean peptide or the like.Without intending to be bound by theory, this second peptide may alsoincrease bioavailability by acting as a protease scavenger thatdesirably competes with the peptide active agent for proteaseinteraction. The second peptide may also aid the active compound'spassage through the liver.

All pharmaceutical compositions of the invention may optionally alsoinclude common pharmaceutical carriers, diluents or fillers. Thecompositions may include gelatin capsules, preservatives, colorants andthe like in their usual known sizes and amounts.

The optional ingredients discussed herein is not exclusive. Otherpharmaceutically acceptable agents may also be included. All optionalcomponents may be combined in any combination. Because most preferencesstated herein provide benefits by different mechanisms, suchcombinations should be beneficial.

Other Optional Preferences

When prepared in tablet form, it is preferred that the maximum weightloss during friability testing be no greater than 1%. As used herein,friability testing refers to the technique described in “TabletFriability”, Chapter 1216, USP 28 page 2745.

When absorption enhancers are used, it is preferred that the weightratio of pH-lowering agent(s) (exclusive of coating on any coated acidparticles being used) to absorption enhancer(s) be between 3:1 and 20:1,preferably 4:1-12:1, and most preferably 5:1-10:1. The total weight ofall pH-lowering agents and the total weight of all absorption enhancersin a given pharmaceutical composition is included in the foregoingpreferred ratios. For example, if a pharmaceutical composition includestwo pH-lowering agents and three absorption enhancers, the foregoingratios will be computed on the total combined weight of both pH-loweringagents and the total combined weight of all three absorption enhancers.

It is preferred that the pH-lowering agent, the peptide active agent(and the absorption enhancer, when used) (whether single compounds or aplurality of compounds in each category) be uniformly dispersed in thepharmaceutical composition. In one embodiment, the pharmaceuticalcomposition comprises granules that include a pharmaceutical binderhaving the peptide active agent, the pH-lowering agent and theabsorption enhancer uniformly dispersed within said binder. In oneembodiment, granules may consist of an acid core, surrounded by auniform layer of organic acid, a layer of enhancer and a layer ofpeptide that is surrounded by an outer layer of organic acid. Granulesmay be prepared from an aqueous mixture consisting of pharmaceuticalbinders such as polyvinyl pyrrolidone or hydroxypropyl methylcellulose,together with the pH-lowering agents, optional absorption enhancers, andpeptide active agents of the invention.

In one preferred embodiment, peptide, acid (preferably coated acid),absorption enhancer, a pharmaceutical binder (when necessary) for drycompression, a disintegrant, a glidant, a stabilizer (when necessary)and a lubricant are all used. Preferably, these materials are thoroughlyintermixed, compressed into tablet form, coated with a water-solublebarrier layer (preferably adding at least 3% to the weight of the tablet(e.g. 3-6%), which is in turn coated with an enteric coating that addsanother 4-10% to the weight of the tablet (e.g. 4-7%). In one preferredembodiment, the water soluble layer adds more than the enteric coating(e.g. 6% and 4%, respectively).

The invention is further illustrated by the following non-limitingexamples.

Example 1

TABLE 1 Composition of Tablets Non-coated Citric acid Coated CitricTablet Acid Tablet mg mg Citric acid powder 500 0 Coated citric acid 0500 Microcrystalline cellulose 112 251 Povidone 25 40 Crospovidone 49 9(disintegrant) Talc 7 0 Magnesium stearate 7 4

Granulated citric acid tablets were prepared by compressing citric acidthat was fluid-bed granulated with citric acid powder, microcrystallinecellulose and povidone with crospovidone, talc and magnesium stearate.Coated citric acid tablets were prepared by compressing glucose-coatedcitric acid with microcrystalline cellulose, povidone, crospovidone andmagnesium stearate.

The dissolution of tablets prepared from both types of citric acid wasmonitored by measuring the amount of citric acid released from eachtablet in a USP dissolution vessel under standard conditions. Theresults in FIG. 1 show that tablets prepared from coated citric acidreleased their contents much more rapidly than tablets prepared fromnon-coated citric acid. Within 10 minutes nearly 60% of the coated acidtablet had dissolved whereas only 20% of the tablet prepared fromnon-coated citric acid had dissolved. By 30 minutes 100% of the tabletprepared from coated citric acid had dissolved, whereas the non-coatedcitric acid tablet required 60 minutes to completely dissolve.

Example 2

TABLE 2 Preferred Tablet Formulation Item mg sCT .2-10 Prosolv HD90 200Citric Acid DC F20 500 Lauroyl-L-Carnitine* 50 Crospovidone 9 KollidonVA64 40 Sodium Pyruvate** 1 Magnesium Stearate 4 *For tablets notcontaining Lauroyl-L-Carnitine add an additional 50 mg of Prosolv HD90.**Sodium pyruvate included when using peptides that can undergomethionine oxidation.Steps for Forming tablet of Table 2

1. High shear or Comill geometrical mixing of peptide such as sCT andProsolv.

2. Add mixed components of step 1 to V blender along with remainingcomponents except magnesium stearate. Mix in V blender.

3. Add magnesium stearate to V blender after step 2 completed. Mix in Vblender briefly.

4. Compress blend into tablets.

5. Coat tablets with subcoat to 6% weight gain.

6. Coat tablets with enteric coat to 7% weight gain.

Example 3

TABLE 3 Stability of Salmon Calcitonin in Tablets Prepared from Coatedand Non-coated Citric Acid Weeks at Room Coated Citric Acid Non-coatedCitric Acid Temperature Percent sCT Recovered 4 103 91 8 98 81 12 98 Notdetermined 24 95 Not determined 36 95 Not determined

Salmon calcitonin was dispersed in tablets prepared from either coatedor non-coated citric acid, povidone, microcrystalline cellulose, talcand magnesium stearate. The tablets were stored at 4° centigrade androom temperature for up to 36 weeks. The sCT content was determined andis summarized in Table 3 as recovery of sCT from tablets stored at roomtemperature relative to tablets stored at 4° centigrade. The results inTable 3 show that there was a trend toward a progressive decrease inamount of sCT in tablets prepared from non-coated citric acid, whereassCT was significantly more stable in tablets prepared from coated citricacid.

Example 4

TABLE 4 Effect of HPMC Undercoat on sCT Cmax L30D-55 HPMC EntericUndercoat coat sCT Cmax % tablet weight gain pg/ml 0 4 70 3 4 142 6 4667 0 7 121 3 7 378 6 7 510

The indicated amount of hydroxypropylmethylcellulose (HPMC) was appliedto tablets that were prepared by mixing salmon calcitonin (1.7 mg)coated citric acid (500 mg), microcrystalline cellulose (Prosolv, 251mg), Kollidon VA64 fine (40 mg), Crospovidone (9 mg) and magnesiumstearate (4 mg) in a V blender, followed by dry compression. Followingapplication of the indicated amounts of HPMC to the indicated weightgain (in those examples utilizing the undercoat), the tablets were thensealed with an enteric coat made of Eudragit L30D-55 to the indicatedfurther weight gain. Beagle dogs were given a tablet of the indicatedcombination of undercoat-enteric coat and aliquots of blood were takenat 15 minute intervals for 4 hours. Plasma was separated from the bloodsamples and analyzed for sCT by ELISA. The peak concentration (Cmax) ofsCT for each combination undercoat-enteric coat is shown in Table 4. Theresults indicate that in the absence of an undercoat the Cmax of sCTincreased 1.7 fold when the amount of enteric coat was increased nearly1.75 fold. When an HPMC undercoat was included, the Cmax of sCTincreased more than 9-fold in one embodiment, and substantially in allembodiments.

Example 5

TABLE 5 Effect of Sodium Pvruvate on PTH(1- 31)NH₂ Stability andRecovery Sodium PTH(1-31)NH₂ Pyruvate Label claim Purity Impurity 1Impurity 2 mg Percent 0 86.8 88.1 3.7 5.4 1 91.3 98.1 0.0 0.0

PTH(1-31)NH₂ (2 mg) and lauroyl-L-carnitine (50 mg) were dispersed intablets prepared as described in Table 2 with and without 1 mg sodiumpyruvate. The tablets were sealed with a non-ionic subcoat and anL30D-55 enteric coat. The PTH(1-31)NH₂ content of the tablets wasanalyzed following their manufacture. The results in Table 5 show thatin the absence of sodium pyruvate there was significant oxidation of thepeptide (impurities 1 and 2) and less than 90% recovery of the expectedamount of PTH(1-31)NH₂. By contrast in the presence of a trace amount ofsodium pyruvate there was no evidence of peptide degradation andrecovery of PTH(1-31)NH₂ was greater than 90%.

Example 6

TABLE 6 Effect of Type of Subcoat on PTH(1-31)NH₂ Cmax in DogsPTH(1-31)NH₂ Cmax Subcoat pg/ml Hydroxypropylmethylcellulose (HPMC) 150Polyvinylpyrrolidone (PVP) 328

PTH(1-31)NH₂ (2 mg) and lauroyl-L-carnitine (50 mg) were dispersed intablets prepared as described in Table 2, sealed to a 6% weight gainwith either an HPMC based subcoat or a PVP based subcoat and a 7% weightgain of L30D-55. Beagle dogs were given an enteric-coated tablet witheither of the indicated types of subcoats and aliquots of blood weretaken at 15 minute intervals for 4 hours. Plasma was separated from theblood samples and analyzed for PTH(1-31)NH₂ by ELISA. The resultssummarized in Table 6 show that PTH(1-31)NH₂ could be orally deliveredto dogs and that there was a 2 fold improvement in plasma Cmax when thesubcoat was made from PVP.

Treatment of Patients

When salmon calcitonin is chosen as active ingredient for treatment ofosteoporosis, periodic administration is recommended. Salmon calcitoninis metabolized quickly with a half-life of only 20-40 minutes followingsubcutaneous administration in man. However, its beneficial effect onosteoclasts is much longer lasting, and may last for more than 24 hoursnotwithstanding rapid decrease in blood levels. There is usually nodetectable blood levels more than two hours after injection of salmoncalcitonin at conventional dosages. Accordingly, periodic administrationof one dose about 5 days per week is preferred. Subcutaneousadministration of salmon calcitonin (100 International units) hasfrequently resulted in peak serum concentration of about 250 picogramsper milliliter. Nasally administered salmon calcitonin (200International units) has proven effective against osteoporosis at peaklevels as low as 10 picograms per milliliter. Some patients reportcertain side-effects such as flushing nausea etc. at high peak levels(e.g. at or above 200 picograms per milliliter). Accordingly, it ispreferred that serum salmon calcitonin peak between 10 and 150 picogramsper milliliter, more preferably between 10 and 50 picograms permilliliter. The serum levels may be measured by radioimmunoassaytechniques known in the art. The attending physician may monitor patientresponse, salmon calcitonin blood levels, or surrogate markers of bonedisease (such as serum CTX I, the C-terminal fragment of type 1 collagenbreakdown), especially during the initial phase of treatment (1-6months). He may then alter the dosage somewhat to account for individualpatient metabolism and response.

The bioavailability achievable in accordance with the present inventionis expected to permit oral delivery of salmon calcitonin into the bloodat the above-identified preferred concentration levels while using only100-1000 micrograms of salmon calcitonin per dosage form, preferably100-400 micrograms, especially between 100 and 200 micrograms.

Regardless of the active agent being administered, it is preferred thata single dosage form (for example, a single capsule or tablet) be usedat each administration because a single capsule or tablet best providessimultaneous release of the polypeptide, pH-lowering agent andabsorption enhancers. This is highly desirable because the acid is bestable to reduce undesirable proteolytic attack on the polypeptide whenthe acid is released in close time proximity to release of thepolypeptide. Near simultaneous release is best achieved by administeringall components of the invention as a single pill or capsule. However,the invention also includes, for example, dividing the required amountof all components among two or more tablets or capsules which may beadministered together such that they together provide the necessaryamount of all ingredients. “Pharmaceutical composition,” as used hereinincludes but is not limited to a complete dosage appropriate to aparticular administration to a patient regardless of whether one or moretablets or capsules (or other dosage forms) are recommended at a givenadministration.

Although the present invention has been described in relation toparticular embodiments thereof, many other variations and modificationsand other uses will become apparent to those skilled in the art. Thepresent invention therefore is not limited by the specific disclosureherein, but only by the claims.

1. A pharmaceutical composition for oral delivery of a physiologicallyactive peptide agent comprising: (A) said peptide agent; (B) at leastone pharmaceutically acceptable acid wherein acid is present in saidpharmaceutical composition in a quantity which, if said composition wereadded to 10 milliliters of 0.1M aqueous sodium bicarbonate solution,would be sufficient to lower the pH of said solution to no higher than5.5; (C) an acid resistant protective vehicle effective to transportsaid pharmaceutical composition through the stomach of a patient whilepreventing contact between said active peptide agent and stomachproteases; and (D) a water soluble barrier layer that separates saidacid from said protective vehicle; wherein either (a) said barrier layeradds 3-6% to the weight of the pharmaceutical composition, exclusive ofany acid-protective vehicle, or (b) said barrier layer comprises amaterial having water solubility in excess of 11 grams per 100milliliters of water at room temperature, or (c) said peptide agent andsaid acid are in the same or only layer of said composition.
 2. Thepharmaceutical composition of claim 1, wherein said barrier layer addsat least 3% to the weight of the pharmaceutical composition, exclusiveof the barrier layer or any layer external thereto.
 3. Thepharmaceutical composition of claim 1, wherein said barrier layer ispresent in an amount which adds between 3 and 6% to the weight of thepharmaceutical composition, exclusive of the barrier layer or any layerexternal thereto.
 4. The pharmaceutical composition of claim 1 furthercomprising an absorption enhancer.
 5. The pharmaceutical composition ofclaim 4, wherein said absorption enhancer is a surface active agent. 6.The pharmaceutical composition of claim 4, wherein said absorptionenhancer is an acyl carnitine.
 7. The pharmaceutical composition ofclaim 4, wherein said absorption enhancer is L-lauroyl carnitine.
 8. Thepharmaceutical composition of claim 1, wherein said acid has a pKa nohigher than 4.2 and has a solubility in water of at least 30 grams per100 milliliters of water at room temperature.
 9. The pharmaceuticalcomposition of claim 1, wherein the acid is selected from the groupconsisting of citric acid, tartaric acid and an acid salt of an aminoacid.
 10. The pharmaceutical composition of claim 1, wherein saidpharmaceutical composition comprises a pharmaceutical binder and,uniformly dispersed in said binder, said acid, an absorption enhancer,and said peptide active agent.
 11. The pharmaceutical composition ofclaim 1, wherein said active peptide is selected from the groupconsisting of salmon calcitonin, natural parathyroid hormone, a parathyroid hormone truncate, and an amidated parathyroid hormone truncate.12. The pharmaceutical composition of claim 11, wherein said activepeptide is PTH1-31-amide.
 13. The pharmaceutical composition of claim 1,wherein said acid comprises acid particles coated with glucose.
 14. Thepharmaceutical composition of claim 1, wherein said acid comprises acidparticles coated with sodium citrate.
 15. The pharmaceutical compositionof claim 1, wherein said acid comprises glucose-coated citric acidparticles.
 16. The pharmaceutical composition of claim 15, whereinaverage particle size of said coated acid particles is between 30 meshand 140 mesh.
 17. The pharmaceutical composition of claim 1 furthercomprising a cellulose filler, wherein said composition has beencompressed into tablet form such that the maximum weight loss duringfriability testing is no greater than 1%.
 18. The pharmaceuticalcomposition of claim 1 further comprising a pharmaceutical binder fordry compression.
 19. The pharmaceutical composition of claim 1 furthercomprising a pharmaceutical disintegrant.
 20. The pharmaceuticalcomposition of claim 1, further comprising a sufficient amount of anantioxidant to substantially prevent oxidation of the peptide agent.21-55. (canceled)